This is where all those scraps of cardboard come in handy. The backs of old notebooks work particularly well.
Read the instructions on the emulsion and activator bottles and follow them carefully to mix them together properly. Pour a little bit of the emulsion onto the screen and spread it as evenly as possible onto the screen. You have to coat both sides. You can scoop the excess back into the pot of emulsion. Don't put it on too thick. You need a thin coat, as even as possible, and on both sides. Try to avoid drips. Again, you don't have to be a perfectionist. Just do your best.
Once you've got the emulsion on there, put the screen in a darkish place to dry. Closets work pretty well. It doesn't have to be totally dark like a photo lab or anything. I like to point a fan at the screen to help it dry faster.
Once it's dry you're going to want to go straight on to the next step so that the emulsion doesn't get exposed and harden completely on your screen. You can touch the screen to feel if it is dry.